Recent advances in miniaturization of various electronic devices have resulted in a widespread use of flexible printed circuit (FPC) boards, which are also referred to as flexible printed wiring boards, for efficiently minimizing the area or space which is necessary to accommodate interconnected electronic circuits. The FPC boards are usually used inside the housing of an electronic device. Because of the restricted space available within such a housing for installing a FPC board, there are limitations imposed on the position where the FPC board may be placed in the housing. Usually, a small electronic device is required to employ a plurality of FPC boards having complex shapes that are bent or folded in a complex pattern so as to fit in the limited space available in the device housing.
Heretofore, if a FPC board is to be bent or folded in use, extra considerations were required when designing the circuit pattern, as well as additional manufacturing processes in order to produce the finished board.
In order to have a flexible board maintain its shape when bent, a rigid support is required. To accomplish this, the copper metal which forms the lead lines can provide the rigid support if there is a large enough area of the copper metal in the portion to be folded. To ensure that a large enough area of copper is provided, many lead lines must pass through the area to be folded. This creates a problem in that the designer must reroute the lead lines through the portion to be folded in order that enough area of copper metal is provided to properly maintain the folded shape. The rerouting of the lead lines requires extra design time and may lead to a layout that is not as efficient as the designer wanted. An increase in the number of lead lines passing through the portion to be folded will result in an increase in the overall width of the portion to be folded since each lead line must be insulated, and thus physically separated from each other.
Additionally, this is followed by removal of a portion of the outside substrate, thus weakening the board and reducing its effective lifetime. The board is then bent and held in the desired shape while a sealant is added to the area where the substrate was removed. The board is then held in the desired shape until the sealant hardens.
Thus extra design work is involved to ensure that the proper concentration of lead lines passes through the area to be folded. Extra manufacturing processes are required in bending the board and maintaining its position while a sealant is added and allowed to dry.
Thus the process to design and manufacture a flexible printed circuit board is time consuming and therefore not very productive.